Stock distribution system



y 1968 w. H. BURGESS, JR 3,385,754

SSSSSSSSSSSSSSSSSSSSS EM WILLIAM H.BURGESS,JR.

y 1968 w. H. BURGESS, JR 3,385,754

STOCK DISTRIBUTION SYSTEM Filed Feb. 11, 1965 2 Sheets-Sheet :1

O O O 0 O 0 Q8 Fig.5

Fi g 3 INVENTOR.

WILLIAM H. BURGESS,JR.

ATTORNEY United States Patent 3,385,754 STOCK DISTRIBUTION SYSTEM William H. Burgess, .lr., Covington, Va., assignor to West Virginia Pulp and Paper Company, New York, N.Y., a corporation of Delaware Fiied Feb. 11, 1965, Ser. No. 431,903 Claims. (Cl. 162299) ABSTRACT OF THE DISCLOSURE A papermaking machine having primary and secondary stock distribution systems including a compact secondary headbox which has a relatively straight flow path therethrough and a downwardly extending nozzle which permits the secondary headbox to be spaced from the forming surface of the papermaking machine. A series of relatively short tubes having inserts therein interconnect the headbox with a tapered manifold, and stabilization of the flow through the headbox may be enhanced by positioning rectifier rolls in the headbox and headbox nozzle.

The present invention is directed to a novel headbox of compact construction and more particularly, to a headbox of the type generally referred to as a secondary headbox.

In the formation of a paper web on a fourdrinier type paper machine conventional procedure is to deposit a dilute suspension of fibers onto an endless, moving, forarninous surface where a major portion of the liquid of the suspension is allowed to drain therefrom leaving a loosely felted mat of fibers. This mat is thereafter subjected to pressing and drying to remove additional liquid and provide a self-supporting paper web. Generally, the deposition of paper stock in this process is accomplished by means of a headbox located adjacent one end of the forming surface.

As is well known in the art, the function of a headbox is to convert the flow of paper stock in the tubular conduits upstream of the headbox to a flat, substantially rectangular configuration for deposition on the forming surface while maintaining the fibers uniformly dispersed throughout the suspension and dampening out eddies, cross fiows, pressure surges and other fiow irregularities. To this end, prior art headboxes usually include an elongated flow path to provide time for flow irregularities to dissipate and one or more expedients, such as expansion chambers, to insure a uniform dispersion of fibers throughout the flow.

Supplementing the process described above, it is often desirable, in the manufacture of certain grades of paper, to deposit additional layers of dilute paper stock onto the partially drained primary layer of stock by means of secondary headboxes located downstream of the primary headbox. Since the secondary headboxes are suspended over the forming surface they must, in addition to providing flow evening and fiber dispersion, be kept as compact as possible. However, since the elongated flow paths, expansion chambers and the like, characteristic of primary headboxes, necessarily result in a large and cumbersome piece of equipment, conventional secondary headboxes usually represent a design compromise; with fiow evening and fiber dispersion qualities sacrificed to some extent in favor of compactness. Thus, in an attempt to provide as long a flow path as possible in the smaller volume available in a secondary headbox, baffies or weirs are often used to effect one or more flow reversals and, in this "ice way, elongate the path of the stock through the headbox.

While this expediency does in fact result in a longer flow path, applicant has found that rather than dampening flow irregularities, the many turns the stock must make in passing through the headbox, in themselves often cause eddies and other undesirable flow patterns. As a result, the jet deposited on the forming surface by the secondary headbox is non-uniform, and thus, often does not provide a uniform coverage of fibers for the base layer and results in a mottled appearance of the finished sheet.

Additionally, since the layer of stock deposited by the primary headbox must pass beneath the secondary headbox, it is desirable to maintain the undersurface thereof spaced from the forming surface. Otherwise the primary stock may splash up on the undersurface of the secondary headbox causing rusting and corrosion thereof. Aside from shortening the life of the headbox, the rust, dried stock and the like will eventually drop off onto the partially drained stock and result in an unacceptable product.

It is therefore, an object of the present invention to provide a headbox which eliminates the deficiencies of conventional secondary headboxes noted above and yet is of unusually compact design and adapted, for the most part, to be spaced from the forming surface a distance suflicient to prevent the buildup of impurities thereon.

As a feature of the present invention, means are provided for dampening pressure surges in the fluid system and maintaining uniform fiber dispersion, in combination with means for preventing undue turbulence or cross fiows from affecting the jet at the slice.

Additionally, the headbox of the present invention eliminates the necessity of acute turns and flow reversals in the flow path and thereby eliminates a source of large scale eddies.

These, and other features and advantages of the present invention will become apparent from the following de tailed description wherein:

FIGURE 1 is a side, elevational view of the wet end of a fourdrinier paper machine incorporating the headbox of the present invention;

FIGURE 2 is a top view of the headbox of the present invention;

FIGURE 3 is a side, elevational view thereof, partly in section;

FIGURE 4 is an enlarged view of a portion of one of the inlet tubes of the present headbox showing the inlet orifice insert; and

FIGURE 5 is a sectional view showing the arrangement of tubes interconnecting the manifold and headbox.

Referring to FIGURE 1 of the drawings, there will be seen a paper machine wet end of, for the most part, conventional construction and including a primary headbox 1 and a forming surface 2, consisting of a foraminous, endless belt 3 supported by a breast roll 4, a couch roll 5, a plurality of table rolls 6 and suction boxes 7.

Dilute paper stock is supplied to the headbox 1 by means of the manifold 8 and, after passing therethrough, is ejected at the slice 9 onto the forming surface 2. As the stock thus deposited travels downstream on the forming surface, liquid is drained therefrom through the forming surface, assisted by the table rolls 6 and suction boxes 7, to form a loosely felted mat of fibers.

Suspended over the forming surface downstream of the primary headbox is somewhat schematically shown, the secondary headbox 10 of the present invention.

As seen in FIGURES 2 and 3, the secondary headbox includes front and back walls 11 and 12, side walls 13 and a top wall 14 defining an upper vat portion of the headbox. At its lower edge, front wall 11 is joined by a filter piece 15 consisting of a downwardly and rearwardly sloped plate member 16 and a downwardly and forwardly sloped plate member 17.

An extension of each of the side walls 13, together with an outlet plate 18 and a downwardly and forwardly sloped bottom wall 19, comprise a lower vat portion 20 in fluid communication with a nozzle portion 21. Nozzle portion 21 includes parallel side walls 22 and parallel, downwardly sloped top and bottom walls 23 and 24. At its lower end nozzle 21 terminates in an adjustable slice assembly 25 including a stationary, lower slice lip 26 and an adjustable upper slice lip 27. As will be apparent to those skilled in the art, gross adjustments of the slice opening may be made by means of the handle 28 and associated linkage while fine adjustment at selected points across the slice is accomplished by the micro-adjustment handles 29.

All of the apparatus thus far described is supported by means of the four, wheeled dollies 39, engaging parallel track members 31 located on either side of the forming surface 2. Thus, since the character of the web produced is affected to some extent by the location of the point at which the secondary layer of stock is deposited, the adaptability of the headbox to be moved a limited distance along the wire provides some degree of control of this variable. Of course, in order to facilitate this movement, the various conduits connected to the headbox, e.g. at the manifold and rotating shower, are formed of a flexible material.

Extending across the rear of the headbox 10, a manifold 32 is provided having parallel, tapered, top and bottom walls 33, a back wall 34 and a front wall 35. Front wall 35 has formed therein throughout its extent a plurality of apertures each receiving the inlet end of a tube 36. The tubes 36are relatively short in length, and as best seen in FIGURE 3, are slightly curved; whereby the upper wall of the manifold 32 is disposed somewhat below the uppermost portion of the outlet ends of the top rows of tubes.

The outlet ends of the tubes 36 are received in a plurality of apertures formed in outlet plate member 18, while adjacent their inlet ends, the tubes are each provided with an orifice insert 37. As best seen in FIGURES 3 and 5, the tubes may be arranged in a plurality of rows, three being shown, with adjacent rows offset with respect to one another; although it will be apparent that other arrangements are possible within the scope of the present invention.

The orifice inserts 37, as best seen in FIGURE 4, are each received in the inlet end of a tube 36 which has been reamed a distance equal to the depth of the insert to form an annular shoulder 38. The insert itself is centrally apertured to provide a straight sided central portion 39 and sloped inlet and outlet portions 40 and 41, respectively.

Within the headbox 10, it will be noted that a rotating shower 42 may be provided in an upper portion of the vat and a series of rectifier rolls 43, 44 and 45 positioned in the flow path from the inlet plate 18 to the slice assembly 25.

In operation, dilute paper stock is supplied under pressure to the manifold 32 at its inlet end 46 from whence it flows toward its outlet end 47. Due to the tapered configuration of the manifold, the pressure at all points along its length may be maintained substantially constant; whereby the dilute stock is supplied to the tubes 36 at nearly equal pressures.

As fluid is tapped off the manifold 32 and enters the tubes 36 it must pass through the orifice inserts 37, where, due to the restricted opening in the central portion 39 thereof, it undergoes a sudden and rapid expansion. This expansion accomplishes two results. First, depending upon the velocity of the fluid in the portion 39 of the insert and the relative cross sectional areas of the portion 39 and the tube 36, the sudden expansion results in an appreciable head loss.

Theoretically, the head loss that will occur in a flow when it abruptly passes from a pipe of one dimension to a pipe of larger cross sectional area may be calculated by the formula:

2 Y5 HL (1 A.) (29) where A, is the cross sectional area of the smaller tube, A the cross sectional area of the larger tube, V is the velocity of the fluid in the smaller tube and g is the gravitational constant.

However, when a flow is allowed to abruptly expand from a smaller to a larger diameter conduit, there is a tendency for the jet issuing from the smaller pipe to remain restricted in cross sectional area for a certain distance downstream of the point of expansion. As a result, the flow does not immediately expand to the full area of the larger pipe as it passes from the smaller. Instead, the major portion of the flow tapers outwardly from the outlet of the smaller tube until it has expanded sufiiciently to conform to the cross sectional area of the larger tube. This results in a relatively stagnant area surrounding the outlet of the smaller tube which would enhance the buildup of air pockets, fiber flocs, and the like.

To remedy this condition, the orifice inserts 37, as seen in FIGURE 4, are tapered outwardly, as at 41, from the restricted portion 39; thereby approximating the shape of the flow as it leaves the restricted portion and substantially eliminating the annularly shaped stagnant area that otherwise would exist.

Of course, modifying the configuration of the expansion point in the fluid path will, to some extent, change the behavior of flow and consequently affect the accuracy of the theoretical formula for head loss given above. Considering this, the fact that the expression will be constant for a given tube-insert combination, and the effect of the pipes themselves on flow conditions, the head loss for a particular tube-insert combination may be expressed:

. V2 H ,-K

where K is an empirically determined constant for a given tube-insert combination and H V and g are as given above.

As will be appreciated by those skilled in the art, by subjecting the flow to a high energy loss in this manner, pressure surges and the like originating upstream of the orifice inserts are substantially neutralized; whereby their ability to effect velocity differentials in the flow is substantially eliminated.

The sudden expansion of flow caused by the inserts 37 produces another desirable phenomena. Thus, as a result of this expansion, an abrupt pressure gradient exists between the portion 39 of the insert and the larger area of the tube 36 immediately downstream of the insert. In this way, turbulence is generated in the flow in each of the tubes and the fibers suspended in the flow maintained well dispersed throughout.

As noted above, as the stock passes through the insert 37, turbulence is created which serves to maintain the fibers uniformly dispersed throughout the liquid. Applicant has found however, that in addition to this beneficial, fine scale turbulence, undesirable, large scale flow fluctuations may occur for a certain distance downstream of the orifice insert, which may be characterized as a tendency of the flow .to alternately attach itself to various portions of the tube wall. It will be apparent that if this turbulent flow were ejected directly into the vat portion of the headbox, undesirable flow patterns would be set up which would carry through to the slice. The tubes 36, therefore, are provided to minimize the tendency of the fluctuations set up 'by the inserts 37 to cause flow irregularities in the headbox vat portion. The tubes of course, serve an additional function. Thus, they both eliminate the cross flows which would be created by turning the stock from the manifold toward the headbox and minimize the effect of the fluctuations created by the inserts 37. However, since the length of tube necessary to accomplish the former will be somewhat less than that required for the latter, it is the latter consideration which governs the minimum permissable length of the tubes 36. Applicant has found this minimum length to be approximately 5 to 6 times the inside diameter of the tube with a length of approximately 9 to 1 serving very satisfactorily.

After passing through the tubes 36, the total flow enters the lower vat portion 20- free of cross flows and the like and with the fibers therein well dispersed throughout. It might be noted at this point that the combination of the short tube and orifice inserts also produces an advantageous result at the exits of the tube 66 which makes it particularly adapted for use in secondary headboxes. Thus, the low flow rates characteristic of secondary headboxes would ordinarily require tubes of relatively small diameters to maintain the velocity in the tubes high enough to prevent settling and fioccing of the fibers and provide suflicient pressure loss to minimize the effect of pressure surges. On the other hand, if small diameter tubes were used they would have to be spaced apart a distance such that uniform blending of the jets as they left the tubes would be difiicult, if not impossible, to achieve. In the present invention, however, fiber dispersion and pressure loss is achieved by means of the orifice inserts 37, thus permitting relatively large diameter tubes to be used. In this manner, the tube outlets may be positioned more closely together than would otherwise be possible, and blending of the jets issuing from the tubes is enhanced. It will be seen therefore, that these two conflicting design considerations are resolved by the use of the short tubes in combination with the orifice inserts.

If desired, a rotating rectifier roll, as at 43, may be provided adjacent the outlets of the tubes 36 to aid in blending the jets issuing therefrom. Additionally, the use of a rectifier roll at this point will provide further head loss, and, prevent the formation of large scale eddies which might result from reflections of the stock flow from the plate 17.

It will also be noted from FIGURE 3 that a second rotating rectifier roll, 44, is positioned in the nozzle portion 21 adjacent its connection to the lower v-at portion 20. As the flow is turned, with the assistance of the filler piece 15, from the lower vat portion to the nozzle, there is a tendency for the stock to separate from the bottom wall 24 of the nozzle. By placing the roll 44 at this point however, this tendency is eliminated and a smooth transition into the nozzle attained.

An additional roll, as at 45, may also be provided adjacent the lower portion of the nozzle 21. As the stock descends downwardly in the nozzle, a portion of the flow may, depending upon the particular operating conditions, become detached from one or the other of the walls 23, 24 by the time the stock reached the lower portion of the nozzle. The use of the rotating, rectifier roll 45 at this point however, serves to maintain a full, uniform flow through to the slice.

From an inspection of FIGURE 3, it will be seen that from the entrance to the vat portion at outlet plate 18 to the slice 25 the stock is not required to turn sharply nor is it subjected to complete flow reversals, which, as noted previously, generate large scale eddies and other undesirable flow patterns. Instead, only comparatively gradual turns are made by the stock as it flows from the outlet plate 18 to the slice 25, aggregating in the range of -95. In a specific installation this has been approximately 10 from the outlet plate to the bottom wall 19, 35 from the bottom wall 19 to the nozzle bottom wall 24, 12 from the wall 24 to the lower slice lip 26 and 33 from the slice lip 26 to the forming surface 2; giving a total degree of turns throughout the flow path of approximately Therefore, the comparatively short, straight flow path, short tubes and orifice inserts combine to provide an etficient distributor system of unusually compact configuration.

It will also be noted from FIGURE 3 that only the slice portion 25 of the headbox is positioned adjacent the forming surface 2. In this manner the tendency for deposits to accumulate on the undersurface of the apparatus is materially reduced along with the attendant corrosion and web contamination described above.

While a preferred embodiment of the invention has been described for purposes of illustration, modifications thereof will be apparent to those skilled in the art within the scope of the appended claims.

I claim:

1. In a paper machine including a breast roll, a couch roll spaced from said breast roll, an endless foraminous belt trained about said rolls and providing a substantially planar forming surface, a primary headbox located adjacent said breast roll and a secondary stock distribution system, including a manifold and a secondary headbox, suspended above said forming surface, extending transversely thereof and located intermediate said rolls downstream of said primary headbox, the improvement comprising said secondary stock distribution system further including:

(a) said secondary headbox having a vat portion, in-

cluding an upper vat portion and a lower vat portion,

(b) said lower vat portion having spaced side walls,

a bottom wall and an apertured plate member forming the rear wall thereof,

(c) a plurality of relatively short tubes extending from said apertured plate member and interconnecting said manifold and said lower vat portion, and

(d) a nozzle portion extending downwardly from said bottom wall of said lower vat portion and terminating adjacent said forming surface.

2. The apparatus of claim 1 further including:

(a) means within said tubes adjacent said manifold for restricting the flow through said tubes.

3. The apparatus of claim 2 wherein:

(a) said lower vat portion, said nozzle and said slice define a continuous stock flow path extending from said tubes to said forming surface, and

(b) the total degree of turns in said stock flow path aggregate 85-9S.

4. The apparatus of claim 3 wherein:

(a) the total degree of turns in said stock flow path aggregate approximately 90.

5. The apparatus of claim 2 wherein said flow restricting means comprise:

(a) an insert received within each of said tubes adjacent said manifold,

(b) each of said inserts having a portion defining an aperture therein of smaller cross sectional area than the internal cross sectional area of the tube within which it is received, and

(c) a sloping portion extending from said aperture defining portion toward the inner wall of said tube.

6. The apparatus of claim 1 wherein:

(a) a rotatable rectifier roll is positioned within said nozzle adjacent said lower vat portion.

7. The apparatus of claim 6 wherein:

(a) a second rotatable rectifier roll is positioned within said lower vat portion adjacent the point of connection of said tubes with said lower vat portion, and

(b) a third rotatable rectifier roll is positioned within said nozzle portion adjacent said slice. 8. The apparatus of claim 1 wherein:

(a) said nozzle includes parallel top and bottom walls and parallel side walls extending between said top and bottom walls,

(b) said nozzle bottom wall joins said lower vat portion bottom wall, and

(c) a filler piece is provided adjacent the upper end of said nozzle top wall extending inwardly of said vat portion.

9. The apparatus of claim 1 wherein:

(a) each of said tubes is approximately five to nine times as long as its inside diameter.

10. A headbox comprising:

(a) a vat portion including an upper vat portion and a lower vat portion having common side walls,

(b) said upper vat portion being substantially rectangular in cross section and terminating at its lower forward edge in a filler piece extending inwardly of the vat portion,

(c) said lower vat portion including an elongated, outlet plate having a plurality of apertures formed therein as a back wall and a downwardly sloping plate member as a bottom wall,

(d) a downwardly sloping nozzle portion including parallel top and bottom walls and parallel side walls, (e) said nozzle portion side walls being coplanar with said vat portion side walls and said nozzle portion bottom wall joining said lower vat portion bottom wall at an angle,

(f) said nozzle portion terminating in a slice assembly including an adjustable upper slice lip and a fixed lower slice lip,

(g) a first rotatable rectifier roll mounted in said lower vat portion adjacent said outlet plate,

(h) a second rotatable rectifier roll mounted in said nozzle portion adjacent the intersection of said lower vat portion and nozzle portion bottom walls,

(i) a third rotatable rectifier roll mounted within said nozzle portion adjacent said slice assembly,

(j) a plurality of tubes having their outlet ends received in the apertures formed in said outlet plate member,

(k) said tubes being at least five times as long as their inside diameters, and

(1) means positioned within said tubes adjacent their inlet ends for restricting the flow into said tubes.

References Cited UNITED STATES PATENTS 2,942,661 6/1960 Beachler l62-299 X 3,119,734 1/1964 Jordan 162-343 X 3,164,513 1/1965 Calehuif 162343 X DONALL H. SYLVESTER, Primary Examiner.

A. C. HODGSON, Assistant Examiner. 

